1. Field of the Invention
The proper performance of almost all electronic and many electro-mechanical devices is critically dependent on the characteristics of the voltage supplied to operate them. Usually, these devices have designed-in tolerance so that a certain amount of distortion in the applied voltage will not affect operation. However, operation degrades very rapidly once the designed-for tolerance for distortion is exceeded. Particularly in recent years, line power has become unreliable in this respect, with severe distortion of its voltage occurring enough to be a cause of major concern in the operation of these devices. Particularly in the case of electronic computers and their associated peripheral gear, it is important that conditions of unacceptably high distortion be detected relatively rapidly so that computation which might otherwise proceed erroneously can be halted with orderly system shutdown procedures until proper line or auxiliary power is available.
Of the various types of distortion, the effect which each has varies from one type of power supply to another. For example, in rectifier power supplies severe in-phase third harmonic distortion or severe peak shift distortion seriously affects the power supply output. On the other hand, out of phase third (and other odd) harmonic distortion does not seriously affect power supply output, even if severe. This is because in rectifier power supplies, the energy in the supply voltage above the proper filter voltage is unaffected by the out of phase third harmonic distortion, but significantly decreased by in-phase third harmonic or peak shift distortion.
2. Description of the Prior Art
The closest art of which applicant is aware is that represented by so-called power line disturbance analyzers as manufactured, for example by Dranetz Engineering Laboratories, South Plainfield, N. J. These devices measure such things as variations in steady state or RMS voltage, sudden changes in individual cycle voltage, spikes, and power interruptions. These kinds of errors will not always cause failure in a rectifier power supply. These deviations in the AC power wave may or may not be an error requiring system shutdown in other kinds of power supplies. The most serious problem, however, with these devices is that the power wave defects mentioned above cannot in many cases be detected by them. U.S. patents in this general area include U.S. Pat. Nos. 3,758,852 (Nowell, et al), frequency detector; 3,401,308 (Darke), current difference sensor between phases of a balanced three phase power wave; and 3,700,919 (Stitch), measuring direction of power flow.